Alternating current system



y 1948- v P. J. WALSH 2,445,897

ALTERNATING CURRENT SYSTEM Filed April 29, 1946 .5 ilk 6 o J a m FIGUREZ FIGURE 'Qb \L cso' FIGURE 4 IN V EN TOR.

Patented July 27, 1948 UNITED STATES PATENT OFFICE- ALTEltNATlNG CURRENT SYSTEM Philip J. Walsh, San Francisco, Calif.

Application April 29, 1946, Serial No. 565,655

7 Claims. (Cl. 171-97) This invention relates to a system for convertiirg direct current into'alternating current.

It is one of the objects of my invention to provide an efficient low cost method for converting direct current into alternating current in a system having no moving parts.

It is another object of my invention to provide a system for converting very low voltage direct current into alternating current at any frequency or voltage.

It is another object of my invention to provide an oscillation generator requiringno electron discharge devices.

It is still another object of my invention to provide an alternating current power multiplier.

My invention possesses many other advantages and has other objects which may be made more easily apparent from a consideration of several embodiments of my invention. For this purpose, I have shown a few forms in the drawings accompanying and forming part of the present specification. I shall now proceed to describe these forms in detail, which illustrate the general principles of-my invention; but it is to be understood that this detailed description is not to be taken in a limiting sense, since the scope of my invention is best defined by the appended claims.

Referring to the drawings:

Figure 1 is a system diagram depicting one form of my invention;

Figure 2 is a drawing for facilitating explanation of the invention;

Figure 3 is a system diagram showing a further modification;

Figure 4 is a system diagram showing a still further modification.

The operation of the system shown in Figure 1 can best be understood by first considering some of the fundamental principles as set forth in Fi ure 2.

Referring to Figure 2, it is seen that current can flow through the circuit comprising battery I, conductor 2, resistor 3, connection l, resistor 5, conductor 6, battery 1, conductor 8 and battery I. With the switches 9 and Ill open as shown in the drawing, the equal series connected batteries l and I produce current flow through the equal series connected resistors 3 and ,5. When the switch III is closed, the value of the current flowingthrough the resistor is doubled while the value of the current flowing through the resistor 3 is simultaneously reduced to zero. This comes about because the batteries II and l are in series assisting relation across resistor 5, but the batteries I l and I are connected in series opposed relation across resistor 3. If the electromotive force developed by battery II is made slightly greater than the electromotive force developed by battery l, closing switch ID not only stops the flow of current through resistor 3 but causes the battery ii to send a small reverse current through the circuit comprising battery I l, resistor 3, conductor 2, battery I, conductor 8, and switch iii to battery ll. If the switch iii is left open and the switch 3 closed, the actions are reversed, that is, the value of the current flowing through the resistor 3 is doubled while all current flow through the resistor 5 is simultaneously stopped.

In Figure 2, I show a source of alternating current 83 connected through a switch it to the primary coil of a transformer I5 having the secondary coil 16 connected to the terminals ll and iii. If the switch M is left open and the switch iii closed, direct current from the two batteries in series flows from the positive terminal of battery 20 thmugh the primary coils 2| and 22 of the transformers 23 and 24 respectively, and back to the negative terminal of battery 25. Since the electromotive force of battery Zll equals that of battery 25 and the coils 2| and Marc equal, no direct current difference of potential exists across the terminals l1 and i8, and therefore, no direct current flows through the coil Is.

Now let us assume that the switch I4 is closed thus applying alternating current potential to the transformer l5 making, at this instant, the terminal l8 positive and the terminal I! negative. Under these conditions the electromotive force developed by the coil I6 is in series assisting relation with the electromotive force developed by the battery 25 and is in series opposed relation to the other secondary coil. By connecting the secondary coils as shown these forces are combined and applied to the single load 26.

During the remainder of the cycle when the terminal I1 is positive and the terminal l8 negative, the electromotive force developed by the coil I6 is in series assisting relation with the electromotive force developed by the battery 20 and is in series opposed relation to the electromotive force developed by the battery 28. By making the peak or maximum electromotive force developed in coil l8 substantially equal to the electromotive force across one or the batteries, such as 28, no

reverse current can flow through the batteries.

Since the coil i8 operates in series with the battery 28 during one half of the cycle and in series with the battery 28 during the other half the cycle it is seen that substantially one half or the altematlng current power dissipated in the load 28 comes from the source l3, the rest being supplied by the batteries 28 and 28. Therefore, the system is an alternating current power multiplier.

Since the alternating current power outputis greater than the alternating current power input it is obvious that some of the power can be fed back from theoutput to the input to sustain continuous oscillations with the source i3 disconnected from the system.

This is preferably done by making the reactance of the condenser 21 equal to the reactance 01' one of the coils, such as 22, at the frequency of the source l3. With the switch 28 closed, the condenser cooperates with the coils 2| and 22 to form a parallel resonant circuit across the terminals i1 and i8. That is, the batteries 28 and 28 operate to prevent the flow of reverse current so that the condenser 21 and coil 22 cooperate to form a parallel resonant circuit during one half of the cycle while the condenser 21 and coil 2| cooperate to form a parallel resonant circuit during the other half of the cycle.

Under these conditions, if the load is small, or disconnected, the'value of the alternating current flowing from the coil I8 into the parallel resonant circuit is very small, Since the alternating current voltage across the load 28 is equal -to the voltage across the source ii, the switch 28 can be closed and the switch l4 opened, these switches being arranged mechanically for simultaneous operation. Feed back current can now flow over the wires 38 and 3| into the transformer II to supply a small current to the parallel resonant circuit across the terminals H and i8 which acts to trigger-oi! energy from the batteries 28 and 28 to maintain the continuous generation of alternating current through the load 28 with the source l3 disconnected from the system.

cuit has a fly-wheel effect and that a very much larger current surges between the condenser 21-- and the coils 2| and 22 than is fed in at the terminals i1 and i8 by the secondary coil i8. When the condenser 21 discharges from terminal i8 through the coil 22 it does so in series with the battery 28 and when it discharges from terminal l'l through the coil 2i it does so in series with the battery 28. That is, the condenser current is always in the direction of the battery voltage.

In Figure 3 I show a two stage system that operates either as an alternating current power multiplier or as a converter. The alternating current source is connected through the switch 38 to the terminals 31. and 38 and supplies alternating current power to the system. The batteries 38 and 48 correspond to the batteries 28 and 28 of Figure 1 and this part of the system together with the transformers 4i and 42 operates in the same manner as the system shown in Figure 1 to produce twice as much alternating current power at the terminals 43 and 44 as ls'fed in at the terminals 31 and 38. This alternating current power is fed into the next stage at the terminals 48 and 48 and combines with the dimeet current power from the batteries 8] and 48 through the coil 81.

minals so and so through the switch 82 to the terminals 81 and 38 some or the output can be fed back to the input to sustain the continuous generation of alternating current from the direct current power furnished by the batteries. The switches 38 and 82 being arranged mechanically so that when the switch 52 is closed the switch 38 snaps open thus allowing feed back current to flow over the wires 53 and 84 from terminals 48 and 88 to terminals 31 and 38. g

In Figure 4, I show a form of the invention using a single transformer 88, and two saturable core reactors 8i and 82 which, make it possible to operate with an alternating current input voltage that is higher than the battery voltage. Otherwise this form of the invention is similar to the form shown in Figure l, the transformer 88 corresponds to the transformer IS, the coils 81 and 68 correspond to the coils 2| and 22, and the batteries 88 and 18 correspond to the batteries 28 and 25.

The actions are best explained by assuming that the switch 85 is closed when the terminal 83 is positive and the terminal 84 negative, the power being supplied by the alternating current source 18. Under these conditions, current flows from the secondary coil H through the coil 88, through the saturable core reactor 82 and through battery 18 to terminal 84. Simultaneously current flows from terminal 83 through coil 81, in the same direction as the current flowing through coil 88, thence through the saturable core reactor 8|, and through batter 88 to terminal 84.

The value of the current flowing through the coils 81 and 8! is very small since it is opposed by the voltage of battery 89 and the high impedance of coil 8|. But the value of the current flowing through the coils 88 and 82 is relatively very large because it is assisted by the voltage of battery l8 and because the core of the coil 82 saturates early in the cycle so that the apparent impedance of coil 82 is very small. The current flowing through the coils 88 and 81 sets up magnetic flux in one direction in the core of transformer 88.

During the other half of the cycle of impressed aiternating current, when the terminal 84 is positive and the terminal 83 negative, the actions are reversed and the coils 81 and 88 set up magnetic flux in the opposite direction in the core of transformer 88. Under these conditions, current flows from coil 'Il through battery 88, coil 8i, coil 81 and to terminal 83. A small current simultaneously flows from terminal 84, through battery I8, coil 82, coil 88 and to terminal 83 because the voltage of battery 18 is opposed to that of coil ll. Since the battery 88 assists the voltage of coil 1! the core of the coil 8| saturates andthe large current now flows The condenser Il' corresponds to the condenser 21 of Figure 1 and operates in the same manner to form a parallel resonant circuit across the terminals 83 and 84.

By transformer action an electromotive force is induced in the secondary coil 12 which supplies power to the load 13. The feed back circuit is similar to that shown in Figure 1, the switch 14 corresponds to the switch i4 and the switch 15 corresponds to the switch 29. By closing the switch 15 and opening the switch M the system continues to produce alternating current in the load 13 with the alternating current source 16 disconnected.

Sources of direct current power other than batteries can be employed, such as dynamos etc. And on the alternating current side, sources of alternating current power such as alternators, vacuum tube oscillators, or mechanical vibrator type circuit interrupters can be used depending upon the purpose to which the system is applied.

I claim:

1. The method of converting direct current energy into alternating current energy comprising applying a fluctuating voltage in opposite phase to each of a pair of direct current sources, and combining in series, the output of both direct current sources as modified by said flutcuating voltage.

2. The method of converting direct current energy into alternating current energy comprising simultaneously applying an alternating current voltage in opposite phase to each of a pair of direct current sources, combining in series, the output of both direct current sources as modifled by said alternating current voltage.

3, In combination, a parallel resonant circuit having two branches and a common branch, a source of direct current in each of said two branches, and means including a source of alternating current potential coupled to said common branch to alternately oppose the flow of current from one of said direct current sources while increasing the flow of current through the other direct current source during each cycle, means combining these efiects in an output circuit, and means feeding back some of the output power to said common branch to sustain continuous oscillations upon removal of said original source of alternating current potential.

4. In combination, a closed circuit comprising a pair of sources of direct current and a pair of windings, means connecting the same in series, a source of alternating current connected between a point intermediate said windings and a point intermediate said sources of direct current for simultaneously reducing the value of the current through one winding and increasing it through the other winding, and means for combining these effects in a work circuit wherein the output power is substantially the sum of the power from said alternating current and direct current sources.

5. Ina system of the character described, a multi-stage power multiplier comprising a plurality of similar stages, each having means for applying a fluctuating voltage in opposite phase to each of a pair of series-connected direct current sources to produce alternating current output power, means for feeding the output power of one stage into the input of the next stage to be combined with more direct current power to produce a greater alternating current output power, and means comprising a load circuit coupled to the final stage.

6. In combination, a closed circuit comprising a pair of sources of direct current, a pair of load elements, means connecting said sources of direct current and said load elements in series, and a source of fluctuating current connected between a point intermediate said load elements and a point intermediate said sources of direct cur- 

